Dead CPU or mobo?

[Nuked Jello]

Running desktop system in sig with Antec Smartpower 500W.

Yesterday, I tried to overclock my Venice CPU to 2.4GHz using "300MHz" mem divider, 3X HTT, and Vcore's from 1.4 to 1.5 but it wasn't quite stable in Windows. So I gave up and set it back to the 2.2GHz, "333MHz" divider, 4X HTT, and 1.4V that I had been running for the past few months. I ran Prime95 for 8 hrs after that, and no errors were reported. Used the PC for another hour or so after that then shutdown and went to work.

When I came back, the PC wouldn't boot. The motherboard LED's would flash once and the fans would all spin once, similar to when you turn off the switch on the PSU and press the power button to discharge the capacitors on the motherboard.

At first, I thought that maybe their was a short somewhere so I removed the motherboard but still no go. I tried using memory sticks one at a time in different slots, although I suspect that it isn't the RAM since from my previous experience with bad RAM, everything will power up but the motherboard will at least beep error codes. I shorted the green and black wires, and the PSU started, so I don't think that's at fault. I also tried clearing CMOS via the mobo jumper.

That leaves me thinking it's either a bad CPU or bad mobo. Can these things die delayed deaths from failed overclocks? But the system was Prime95 stable when I set back to my previous settings ... only to fail some 12 hours later?

Is there any way to isolate which is at fault without CPU or mobo swaps?

Or maybe I overlooked something else?

Thanks for your help!

 

[rysher]

u tried the psu, yes it works but can it give the system enough power?
try it w/ another psu.
mobo light turns on, mobo is not dead.
no beep codes, when no cpu is found there is 1 short and 2 long beeps.
i'd try another psu if i were u. if that won't fix it i'll look at the mobo, and start troubleshooting from there.

 

[Chernobyl1]

yeah, if you cant find the fault by inspection you will need to try your kit in someone elses PC or vice versa.

 

[Nuked Jello]

Thanks for the suggestions, I guess I'm looking at a bad PSU or mobo right now.

I am using the bare minimum needed to POST at the moment: CPU+HSF, single stick of RAM, video card, mobo and PSU.

Since the mobo's lights only flash once then turn off, I assume CPU or RAM are not at fault because if those were bad at least the motherboard would power up - as in all fans should start spinning constantly + mobo LED's stay on and beep error codes at me. Same situation for video card I believe.

Since I don't have a spare 24-pin PSU or s939 mobo, I need to find a local shop that will help diagnose PSU and mobo for a reasonable fee ...

 

[Chernobyl1]

It could be a fault with any component causing the PSU to trip.
for example, if a memory stick had a short on the power rails, that would be sensed and the PSU would cut power.

The flash you see is how long the PSU takes to sense the problem.

 

[Nuked Jello]

Interesting, I had no idea a memory stick could short power rails. I did try a different slot and a different stick. I will try to see if something is stuck in one of the slots although I find that quite odd when I didn't even touch the insides of the computer before it wouldn't boot.

After some googling and reading the manual, I finally realized the motherboard's LED's aren't for looks. Epox calls it "LEDION" and one will light up for each of the CPU / DIMM / video if they are functioning correctly. When I press the power switch, the DIMM and video ones flash briefly but the CPU one does not. So I guess I cannot rule out the CPU afterall.

So my newest question is, if the CPU is dead, will the motherboard (Epox 9npa+ in particular) always at least power up and give me beeps like rysher indicated above?

The thermal paste on the CPU is the stock Arctic Cooling goop that came with the Freezer 64 Pro. They claim it is not electrically conductive so I don't think that will cause a short. But I guess it wouldn't hurt to try reseating the CPU.

 

[Chernobyl1]

Check the manual to see if there are any error beep codes associated with the CPU not functioning. If there are beep codes its likely you should expect some with the CPU removed.

If the PC does the same trick of not powering up at all with the CPU removed, its probably something else.
I cant easily test this though so if I'm wrong can someone say.
And if a PC indeed doesnt normally power up with the CPU removed, please let us know.

The chance of a memory chip, circuit board or component having a short is very slim indeed but when the trail points in that direction, its a good to consider it. I used that as an example

I hope you can get another CPU to try.